I believe Springfield’s local radio station KBBL 102.5 is first mentioned in episode 13 from season 1 called “Some Enchanting Evening” but this design comes from season 5 episode 17 aptly called “Bart Gets an Elephant”. If you wear this some might actually demand an elephant from you.

Here’s the link to the product as a sticker, but you can view the design on multiple items if you’re interested.